The present invention relates to a heat source for delivering a pulse of heat by combustion of a metered amount of liquid fuel. More particularly, the invention relates to a miniature heat source for use in portable devices where a controlled pulse of heat is desired.
Fuel igniting devices are disclosed in U.S. Pat. Nos. 4,247,283; 4,856,981; 4,891,003; and 5,127,822. Of these, the ""283 patent relates to a flaming trumpet which emits a flame under the control of the musician playing the instrument, the ""981 patent relates to a pulse combustion burner connected to a tailpipe or exhaust pipe, the ""003 patent relates to a pulse combustion device connected to a tailpipe, and the ""822 patent relates to a combustion apparatus for various heating applications.
U.S. Pat. Nos. 3,242,700 and 5,274,214 relate to cigarette lighters. The ""700 patent discloses a lighter which includes a sparking wheel and an ignitable fuel. The ""214 patent discloses a battery powered lighter which includes a resistance heating element.
U.S. Pat. Nos. 4,694,841; 4,774,970; 4,854,331; and 5,179,966 disclose various tobacco smoking devices. The ""841 patent is a system for self lighting cigarettes using substances which react with each other, the ""970 patent discloses a device which includes a conventional gas lighter, the ""331 patent discloses a smoking article wherein a carbonaceous fuel element is used to heat a tobacco flavor medium, and the ""966 patent discloses a smoking article which utilizes an electrically heated element to heat a tobacco flavor medium. Another type of smoking device is disclosed in European Patent Publication No. 858744 wherein heat from a combusted gas heats a heat exchanger which raises the temperature of a tobacco containing substance to generate flavor without burning the substance.
A limitation of battery powered heat sources is that it is necessary to recharge the battery or replace it with a non-rechargeable battery after a certain period of use. A disadvantage of liquid fuel heat sources is that the fuel can be wasted since it is not metered. Accordingly, it would be desirable if a heat source were available which obviates the need to recharge or replace the battery of a battery powered heat source. It would also be desirable if such a heat source could produce a consistent pulse of heat corresponding to the specific heat needs of the application in order to prevent the waste of fuel.
The invention provides a miniature heat source for delivering a metered pulse of fuel which can be converted into heat, as disclosed by the various preferred embodiments of the invention. The miniature heat source of the present invention is ideally suited to be implemented in an environment where a high energy pulse of heat is desired. For example, it is contemplated that the heat source could be used within a portable, hand-held device for smoking tobacco or used as part of an electricity generating micro-turbine.
In one embodiment, the invention provides a miniature heat source for providing a pulsed amount of heat, the heat source comprising a housing which includes a combustion chamber, a valve member and a liquid fuel source. The fuel is preferably mixed with air and supplied to the combustion chamber as a combustible gas which passes through a venturi arrangement and the combustible mixture can be ignited and/or catalytically reacted to produce heat. When the heat source is used in a smoking device, the heat from the combusted fuel can be transferred to a heat transfer member which heats tobacco sufficiently to allow smoking thereof.